The circulatory system is made up of the heart, blood, and blood vessels. The heart pumps oxygen-rich blood throughout the body via the arteries and returns oxygen-depleted blood to the lungs and heart via the veins. Some key facts about the cardiovascular system are that the adult heart pumps nearly 4,000 gallons of blood per day and beats about 30 million times per year. Common medical tests used to diagnose heart conditions include exercise stress tests, Holter monitors, electrocardiograms, and cardiac catheterizations. Major cardiovascular diseases include atherosclerosis, coronary artery disease, hypertension, and stroke. Preventing cardiovascular disease involves controlling risk factors like smoking, high blood pressure, high cholesterol, lack of physical activity, and obesity.

1. Cardiovascular System By: Anne Cozzi

3. Made up of the heart, blood and blood vessels, the circulatory system is your body's delivery system. Blood moving from the heart, delivers oxygen and nutrients to every part of the body. On the return trip, the blood picks up waste products so that your body can get rid of them.

5. Your heart About the size of your clenched fist, your heart is a muscle. It contracts and relaxes some 70 or so times a minute at rest -- more if you are exercising -- and squeezes and pumps blood through its chambers to all parts of the body. And it does this through an extraordinary collection of blood vessels.

7. Your blood travels through a rubbery pipeline with many branches, both big and small. Strung together end to end, your blood vessels could circle the globe 2 1/2 times! The tubes that carry blood away from your heart are called arteries. They're hoses that carry blood pumped under high pressure to smaller and smaller branched tubes called capillaries. The tubes that more gently drain back to the heart are veins.

9. When you inhale, you breathe in air and send it down to your lungs. Blood is pumped from the heart to your lungs, where oxygen from the air you've breathed in gets mixed with it. That oxygen-rich blood then travels back to the heart where it is pumped through arteries and capillaries to the whole body, delivering oxygen to all the cells in the body -- including bones, skin and other organs. Veins then carry the oxygen-depleted blood back to the heart for another ride.

11. Most of your blood is a colorless liquid called plasma. Red blood cells make the blood look red and deliver oxygen to the cells in the body and carry back waste gases in exchange. White blood cells are part of your body's defense against disease. Some attack and kill germs by gobbling them up; others by manufacturing chemical warfare agents that attack. Platelets are other cells that help your body repair itself after injury.

13. The body of an adult contains over 60,000 miles of blood vessels!

15. An adult's heart pumps nearly 4000 gallons of blood each day!

17. Your heart beats some 30 million times a year!

19. Medical Diagnostic Tests

21. Exercise Stress Test The exercise stress test, also known as the treadmill test or exercise tolerance test, indicates whether your heart gets enough blood flow and oxygen when it's working its hardest, such as during exercise. Often, stress tests are given to people with chest pain or other symptoms who appear to have coronary artery disease, based on a medical exam and EKG. In addition, these tests are sometimes used for other purposes, from assessing the effectiveness of heart disease treatment to gauging the safety of a proposed exercise program. Stress tests are among the best tools for diagnosing heart disease, and some research suggests that they may also be useful in estimating disease risk in people who don't have symptoms but have risk factors such as high cholesterol. If you are over age 40 and are at risk for coronary artery disease because you smoke or have high blood pressure or other risk factors, ask your doctor if you should have this test.

23. Holter Monitor A Holter monitor is a portable EKG device that records your heart rhythm over time, outside the hospital or doctor's office. Whereas a regular EKG examines your heart's electrical activity for a few minutes, the Holter monitor examines changes over a sustained period of time-usually a 24- to 48-hour period-while you go about your daily activities and even while you sleep. Doctors use it to evaluate symptoms that come and go and that might be related to heart-rhythm changes.

25. Electrocardiogram The coordinated pumping of your heart is controlled by natural electrical currents within the heart. An EKG (sometimes referred to as ECG) measures those currents. An EKG is especially useful for diagnosing heart attacks and rhythm abnormalities, but it can also provide many clues about other conditions. You should have an EKG every one to three years after age 40 if you have heart disease; if you are at risk for developing it because you have high blood pressure, high cholesterol, or diabetes; or if you are about to start a vigorous exercise program.

27. Cardiac Catheterization Cardiac catheterization with coronary angiogram takes pictures of the blood vessels in your heart, to evaluate the health of your heart and detect any narrowing of the blood vessels or other problems. The catheterization is performed by a cardiologist (or sometimes a radiologist) who is a specialist in doing this type of test.

29. Diseases of the Heart

30. Atherosclerosis Atherosclerosis, or hardening of the arteries, is the cause of more than half of all mortality in developed countries and the leading cause of death in the United States. When the coronary arteries are involved, it results in coronary artery disease (CAD). The hardening of the arteries is due to the build up of fatty deposits called plaque, and mineral deposits. As a result, the supply of blood to the heart muscle (myocardium) is reduced and can lead to ischemato the heart, causing chest pain or a myocardial infarction . The hardening of the arteries causes an increase in resistance to blood flow, and therefore an increase in blood pressure. Any vessel in the body may be affected by atherosclerosis; however, the aorta and the coronary, carotid, and iliac arteries are most frequently affected. The process begins early in life. Therefore, physicians should obtain risk-factor profiles and a family history for children.

31. Cardiovascular Disease Cardiovascular disease (CVD), and the resulting complications, is the main cause of death for both males and females in the United States and other technologically advanced countries of the world. It usually is in the top five causes of death in lesser-developed countries. Diseases of the cardiovascular system include those that compromise the pumping ability of the heart, cause failure of the valves, or result in narrowing or hardening of the arteries. In addition, toxins and infectious agents may damage the heart and blood vessels. Injury or failure of the cardiovascular system, especially the heart, also will affect the peripheral tissues that depend on the delivery of nutrients and the removal of wastes through the blood vascular system. CVD is a family of diseases that includes hypertension , atherosclerosis , coronary heart disease , and stroke .

32. Hypertension Blood pressure is a measure of the force of blood against the walls of arteries. It is recorded as two numbers: the systolic pressure over the diastolic pressure. Systolic pressure is the pressure as the heart beats, while diastolic pressure measures the pressure when the heart relaxes between beats. Blood pressure is normally measured at the brachial artery with a sphygmomanometer (pressure cuff) in millimeters of mercury (mm Hg) and given as systolic over diastolic pressure. Normal blood pressure is less than 120 mm Hg systolic and less than 80 mm Hg diastolic—usually expressed as "120 over 80." However, normal for an individual varies with the height, weight, fitness level, age, and health of a person. Blood pressure is normally maintained within narrow limits, but it can drop during sleep or increase during exercise. Hypertension (HTN), or high blood pressure, occurs when the force of blood passing through blood vessels is above normal. The increase in pressure forces the blood to hit the blood vessel walls. HTN is called "the silent killer" because many people do not know they have the condition. Consistently high blood pressure increases the risk for a stroke or a heart attack .

33. Coronary Artery Disease Coronary artery disease refers to any of the conditions that affect the coronary arteries and reduces blood flow and nutrients to the heart. It is the leading cause of death worldwide for both men and women. Atherosclerosis is the primary cause of CAD. Controlled risk factors associated with CAD include hypertension, cigarette smoking, elevated blood lipids , a high-fat diet , physical inactivity, obesity, diabetes , and stress. Lifestyle changes can assist in prevention of CAD. Uncontrolled risk factors include a family history of CAD, gender (higher in males), and increasing age.

34. Stroke Strokeoccurswhen the brain does not receive sufficient oxygen-rich blood through blood vessels or when a blood vessel bursts. A stroke may result from blockage of the blood vessels due to a blood clot or from ruptures of the blood vessels . Uncontrolled hypertension is a major risk factor for strokes

35. Preventing CVD The symptoms of CVD develop over many years and often do not manifest themselves until old age. Autopsies of young servicemen indicate significant accumulation of plaque and hardening of the arteries (atherosclerosis). Thus, primary prevention for CVD must begin in early childhood. Preventing premature CVD (before age 60) is crucial. Heart attacks between the ages of forty and sixty are primarily due to lifestyle factors. Smoking, high blood cholesterol, high blood pressure, and lack of physical activity are the most serious risk factors for CVD and heart attack. Controlling one of these risk factors can help control others. For example, regular exercise can help control cholesterol, blood pressure, weight, and stress levels. Smoking is the most preventable risk factor. Smokers have twice the risk for heart attack that nonsmokers have. Tobacco use alters the blood chemistry and increases blood clotting . Nearly one-fifth of all deaths are due to tobacco use, and a smoker lives an average of seven to eight fewer years than a nonsmoker. The worldwide increase in obesity and type 2 diabetes (in both children and adults) point to a high-fat, high-calorie diet and a sedentary lifestyle. Poverty increases the risk for poor dietary habits and poor access to healthful foods.